The following description of background art may include insights, discoveries, understandings or disclosures, or associations together with dis-closures not known to the relevant art prior to the present invention but provided by the invention. Some such contributions of the invention may be specifically pointed out below, whereas other such contributions of the invention will be apparent from their context.
OFDM (orthogonal frequency division multiplexing) is a form of FDM where carrier signals are orthogonal to each other. Thus cross-talk between sub-channels is eliminated. Since low symbol rate modulation schemes suffer less from inter-symbol interference caused by multi-path propagation, a number of low-rate data streams are transmitted in parallel instead of a single high-rate stream. Since the duration of each symbol is long, a guard interval may be inserted between the OFDM symbols, thus eliminating the inter-symbol interference. A cyclic prefix transmitted during the guard interval comprises the end of the OFDM symbol copied into the guard interval, and the guard interval is transmitted followed by the OFDM symbol.